The API 5CT standard covers seamless and welded casing and tubing pipes for upstream operations (OCTG = oil country tubular goods). Casing pipes are available in the diameter range 4 1/2 . to 20 inches, and in the following materials: H-40 / J-55 / K-55 / N-80 / L-80 / C-90/ T-95 / P-110 /